diff --git a/docs/plugins/gst_plugins_cache.json b/docs/plugins/gst_plugins_cache.json
index f14d6285..11bf5b56 100644
--- a/docs/plugins/gst_plugins_cache.json
+++ b/docs/plugins/gst_plugins_cache.json
@@ -1888,7 +1888,7 @@
                         "writable": true
                     },
                     "fragment-duration": {
-                        "blurb": "Duration for each FMP4 fragment",
+                        "blurb": "Duration for each FMP4 fragment in nanoseconds",
                         "conditionally-available": false,
                         "construct": false,
                         "construct-only": false,
diff --git a/mux/fmp4/src/fmp4mux/imp.rs b/mux/fmp4/src/fmp4mux/imp.rs
index 3a090d6d..6da92b91 100644
--- a/mux/fmp4/src/fmp4mux/imp.rs
+++ b/mux/fmp4/src/fmp4mux/imp.rs
@@ -2827,7 +2827,7 @@ impl ObjectImpl for FMP4Mux {
             vec![
                 glib::ParamSpecUInt64::builder("fragment-duration")
                     .nick("Fragment Duration")
-                    .blurb("Duration for each FMP4 fragment")
+                    .blurb("Duration for each FMP4 fragment in nanoseconds")
                     .default_value(DEFAULT_FRAGMENT_DURATION.nseconds())
                     .mutable_ready()
                     .build(),